The picture is normally related the card. Notice how you never see pictures of fallen on cards about the traveler. Shin Malphur was a Hunter. There's a picture of a Hunter on his cards. It brings about the question, why would Dredgen Yor's cards be any different?

Yeah, a warlock was on the card, but so was the gun it was about, Thorn. They may have chosen the warlock simply because it was the easiest class to complete the bounty on.